As shown in FIG. 1, a conventional probe card is composed of a PCB (Printed Circuit Board) 230 connected to a test head that functions to transfer an electrical signal from a tester, a multilayered ceramic substrate 210 positioned under the PCB 230 and electrically connected thereto by a plurality of fine interface pins 233, jigs 232 for mechanically holding the PCB 230, the plurality of interface pins 233, and the multilayered ceramic substrate 210, and a plurality of probe needles 200 attached to the lower surface of the multilayered ceramic substrate 210 to be in contact with an electronic and electric device.
The probe needle 200 is formed in a manner such that a probe needle base formed of conductive metal and a polymer elastomer 240 are formed on the ceramic substrate 210 through photolithography using a photoresist, after which the conductive metal is continuously laminated on the probe needle base to be supported by the polymer elastomer 240, thus forming a probe needle tip 250.
As shown in FIGS. 2 and 3, the method for forming the probe needle includes,
a first step of depositing a seed layer 120 on a multilayered ceramic substrate 110, applying a photoresist 130 on the seed layer, and then baking it; a second step of exposing and developing the photoresist according to the pattern of a mask, thus forming an island type probe needle base; a third step of etching the seed layer 120 corresponding to an exposed region after removal of the photoresist in the second step; a fourth step of embedding the exposed portion with a polymer elastomer 140; a fifth step of depositing a seed layer 160 on the polymer elastomer, applying a photoresist 131 on the seed layer, and then baking it; a sixth step of patterning the photoresist in a desired shape according to the pattern of a mask through exposure and development, and then plating the exposed portion with a conductive metal 170 composed of a nickel alloy; a seventh step of applying a photoresist 132 on the layer formed in the sixth step, baking it, radiating light onto the photoresist to develop the photoresist into a desired shape, and then plating the exposed portion with a conductive metal 171 composed of a nickel alloy; an eighth step of applying a photoresist 133 on the layer formed in the seventh step, baking it, radiating light onto the photoresist to develop the photoresist into a desired shape, and then filling the exposed portion with a conductive metal 172 composed of a nickel alloy; a ninth step of applying a photoresist 134 on the layer formed in the eighth step, baking it, radiating light onto the photoresist to develop the photoresist into a desired shape, and then filling the exposed portion with a conductive metal 173 composed of a nickel alloy, thus forming a probe needle tip of a probe needle; and a tenth step of removing the seed layers and the photoresists from the polymer elastomer so that only the conductive metals constituting the probe needle remain.
As such, a plating process is conducted using the conductive metal, after which a surface flattening process is conducted using a grinder and a polisher, and then subsequent procedures are performed.
In addition, in the case where the probe needle tip of the conventional probe needle is formed into a multilayer configuration, procedures of plating the portion exposed through exposure and development with the nickel alloy as the conductive metal and then evenly polishing the nickel alloy are carried out.
However, as described above, upon continuous lamination of the photoresist layers, it is impossible to polish the third and subsequent photoresist layers because of irregular removal or flexibility of the photoresist layer.